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Howler monkeys may owe their color vision to leaf hue

Distinguishing red from green makes healthier leaves stand out

MONKEY BUSINESS Being able to tell red and green apart helps howler monkeys like this one pick out younger, more nutritious leaves, research suggests.

Lorraine Logan/Shutterstock

BOSTON — A taste for reddish young leaves might have pushed howler monkeys toward full-spectrum color vision. The ability to tell red from green could have helped howlers pick out the more nutritious, younger leaves, researchers reported February 19 at the annual meeting of the American Association for the Advancement of Science. That’s a skill their insect-eating close relatives probably didn’t need.

Primates show substantial variation in their color vision capabilities, both between and within species, said Amanda Melin, a biological anthropologist at the University of Calgary in Canada. Trichromatic vision (how most humans see) requires three light-sensitive proteins in the eye that can detect different wavelengths of light. Within most monkey species in Central and South America, only some individuals have trichromatic vision. Males have dichromatic vision —

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